This infiltration is happening in churches which have real estate owned in common by the denomination, rather than by individual congregations. That is why I think a large portion of this is about money.
As far as the Catholic Church, I think an attempt WAS made to take it over, back in the seventies and 80's. The rise of EWTN and Mother Angelica, as well as the election of Pope Benedict, has stopped a lot of the nonsense. There are still dioceses where weird stuff happens (Los Angeles being one) but it seems to me that a lot of things are being corrected.
I also don't understand why they reserve communion for the ministers since it is symbolic. I only went to a Presbyterian church a couple of times so I don't know too much about them.
The Catholic church's biggest problem was the deal with the devil it made by allowing homosexuals into the priesthood starting in the 60s... most of the problems in the US can be traced directly back to this decision.
Once they were in, they started trading sex for favor and power and austracizing anyone who stood up to them. The Dioceses that have been harmed the most are the ones where this influence grew the most, Boston, LA etc...
Benedict needs to purge these diocese rapidly and fully, and yes it will mean some very high ups in them will be forced out.. but it needs to be done.